Ozone Hole Science Revisited
Ronald Bailey | September 27, 2007, 10:02am
Scientists are commemorating the discovery 20 years ago that man-made chlorofluorocarbons (CFCs) used chiefly in refrigerators and air-conditioners were responsible for creating the "ozone hole" over the Antarctic. The scientists concluded that CFCs would drift into the stratosphere where they would produce chlorine compounds that react with ice particles and sunlight to efficiently destroy ozone molecules that shield the surface from ultraviolet light streaming from the sun. In 1987, the world adopted the Montreal Protocol to eventually eliminate the production of CFCs. Activists often cite the Montreal Protocol as a model for a future treaty addressing man-made global warming by banning the emission of greenhouse gases. A Nobel Prize in chemistry was awarded in 1995 to the three scientists who identified the ozone/CFC connection.
This neat story of the scientific identification of a man-made cause for stratospheric ozone depletion followed by a successful international response to the threat is now being challenged by some very recent research. News@nature.com (sub required) is reporting a new analysis by Markus Rex, an atmosphere scientist at the Alfred Wegener Institute of Polar and Marine Research in Potsdam, Germany, which finds that the data for the break-down rate of a crucial molecule, dichlorine peroxide (Cl2O2) is almost an order of magnitude lower than the currently accepted rate.
What this could mean according to the Nature news article is that:
"This must have far-reaching consequences," Rex says. "If the measurements are correct we can basically no longer say we understand how ozone holes come into being." What effect the results have on projections of the speed or extent of ozone depletion remains unclear.
The rapid photolysis of Cl2O2 is a key reaction in the chemical model of ozone destruction developed 20 years ago2 (see graphic). If the rate is substantially lower than previously thought, then it would not be possible to create enough aggressive chlorine radicals to explain the observed ozone losses at high latitudes, says Rex. The extent of the discrepancy became apparent only when he incorporated the new photolysis rate into a chemical model of ozone depletion. The result was a shock: at least 60% of ozone destruction at the poles seems to be due to an unknown mechanism, Rex told a meeting of stratosphere researchers in Bremen, Germany, last week.
Other groups have yet to confirm the new photolysis rate, but the conundrum
is already causing much debate and uncertainty in the ozone research community. "Our understanding of chloride chemistry has really been blown apart," says John Crowley, an ozone researcher at the Max Planck Institute of Chemistry in Mainz, Germany.
"Until recently everything looked like it fitted nicely," agrees Neil Harris, an atmosphere scientist who heads the European Ozone Research Coordinating Unit at the University of Cambridge, UK. "Now suddenly it's like a plank has been pulled out of a bridge." ...
Nothing currently suggests that the role of CFCs must be called into question, Rex stresses. "Overwhelming evidence still suggests that anthropogenic emissions of CFCs and halons are the reason for the ozone loss. But we would be on much firmer ground if we could write down the correct chemical reactions."
Of course, it may be that Rex's research has gone wrong somehow or that another chemical mechanism involving CFCs will turn out to be chiefly responsible for ozone depletion. Nevertheless, it is good to keep in mind that all scientific results are provisional and may change in the light of new evidence.
By the way, for anyone who cares about my own take on the ozone hole/CFC issue, in chapter 8 of my 1993 book, Eco-Scam: The False Prophets of Ecological Apocalypse, I concluded:
Despite a great deal of continuing scientific uncertainty, it appears that CFCs do contribute to the creation of the Antarctic ozone hole and perhaps to a tiny amount of global ozone depletion. If CFCs were allowed to build up in the atmosphere during the next century, ozone depletion might eventually entail significant costs. More ultraviolet light reaching the surface would require adaptation—switching to new crop varieties, for example—and it might boost the incidence of nonfatal skin cancer. In light of these costs, it makes sense to phase out the use of CFCs.
John Blake | September 28, 2007, 9:49am | #
Context and perspective govern here, as in all else. First: What is the pattern of Antarctic "ozone holes" over (say) AD 1325 - c. 1875 (the Little Ice Age)? If this is a cyclical, recurring phenomenon, it cannot be anthrogenic. If data is not available, meaning "we don't know", speculative hypotheses are meaningless.
As with the "Hockey Stick" graph and NASA's Soros-funded disinformation debacle on global temperature from about 1930 [a ridiculously short time-frame], both debunked by Steven McIntyre, this Ozone Depletion schtick reeks of alarmist eco-whelps.
What partisan propagandists all ignore is that objective reality governs natural processes. Over some 10-million years, due primarily to plate-tectonic dispositions (continents walling off Eastern from Western hemisphers), glaciations have come and gone with clockwork precision, averaging 11,500 - 12,500 years between.
Depending on how one counts the Younger Dryas, Earth today is 1,500 years overdue to end our current interglacial, which should have terminated with the Roman Empire. In 2113 we shall intersect an annular ring of intra-solar dust, as happens every 800 years. Last episode occurred in 1313, when 10 - 12 years of failed harvests tipped every civilized culture on the planet to destruction (think Black Death, Mongol hordes, drought and pestilence).
Anyone, researcher or layman, who takes inflated "ozone hole" prognostications seriously is either dishonest or a fool.
Kurmudge | September 28, 2007, 4:49pm | #
As always, there is an in-between answer that doesn't cost all that much on balance, and is a decent solution. We still don't know, even with the latest data, how much of an issue CFCs were in the seasonal thinning of atmospheric ozone at the pole (there was never a "hole"), and indeed, there are and always were good reasons to be mildly skeptical of the apocalyptic reports.
But if you look back, there were an awful lot of needless releases of CFCs, that didn't cause much difficulty when banned, and a bunch of other virtually no-risk, or minimal impact, applications that should not have been banned.
Spray can propellants for hair spray, paint, deodorant, etc., blew a lot of the stuff into the air for no particular good reason, and the substitutes are really not an issue. We all get along fine today with pump sprays and other propellant approaches. CFCs were used in open systems all over as industrial solvents, for cleaning printed wiring boards after wave soldering, and we have replacement approaches now that do an OK job.
But CFCs should never have been banned in closed system refrigerators, it would have been good enough to simply require that when junking a refrigeration unit the coolant be recovered before disposal, along with improving the leak characteristics of auto units (heck, as a consumer I want that fixed, auto ACs leak way too much for no great reasons). Nor should they have been banned in medical inhalers for the reasons cited (I have asthma myself), the release volume involved was meaningless- just another "green feel-virtuous" opportunity for Federal regulators. And, sorry folks, DuPont did indeed (still does) do very well on CFC-134 now that the generic competition of good old Freon is gone.
This story is very similar to that of DDT- there was a potential issue, and the big government people used it to make life worse on balance and grab more power, when some modest controls on external environmental usage would have resolved virtually any actual problem.
And there are a hundred other stories in the Naked City just like these...
JM Hanes | September 28, 2007, 5:37pm | #
J:
"In light of these costs, it makes sense to phase out the use of CFCs"
In the future, you might want to change that to 'phase out the UNNECESSARY use of (fill in name of evil chemical created to destroy humanity in the name of corporate profit)'.
Alas, it's tough to drum up widespread support for anything resembling half-measures. Brian Eno offered up the best take on the political realities I've ever heard:
The central problem of politics: Do you paint simplistic pictures that make people act (and leave them with too simplistic a view of the world) or do you paint baffingly shaded and contingent scenes that leave people paralyzed by indecision?
J sub D
You have to understand that the earth was at the optimal temperature and there was a complete "balance" of nature until humans ...
Could you please tell me what the optimal earth temperature is and how is that determined?
I'm nobody's green giant, but I don't think there's any reason not to use the obvious fact that human life is sustainable at the current
status quo as a working baseline. With the advent of the atom bomb, we began the ongoing process of absorbing and examining the idea that we may actually be powerful enough to alter underlying global dynamics, whether inadvertantly or purposefully, to potentially devasting, and perhaps most disturbingly, to potentially unknown or unpredictable effect.
I also don't think it's all that hard to define a fairly narrow range of conditions, within the global continuum, under which human existence is possible. Considering how much of that range would be inimicable to life as we know it know it now, I'm not why sure a lot of folks so archly dismiss concern about global trends, just because such changes may be natural and not man-made. The flip-side of destructive power, of course, is its potentially constructive use. While we don't really know for sure whether we've initiated or affected global
warming climate change, or not, perhaps we should all be hoping that we can -- just in case the thermometer, as only one obvious example, starts taking the kind of nosedive that the
big picture timeline suggests is otherwise inevitably in store.
There are certainly some negatives in the current fear/guilt/faith based environmental politicking, but I suspect the attention also generates more $$ for research, so it may end up being a net plus. It's my impression that you could hardly find any money for weather modelling a decade or so ago, and a lot of the climate related science has short as well as long term benefits.
J. H. Colter | September 29, 2007, 4:45pm | #
OK, someone please help me with my memory. In p-chem in the late 1970s, we learned that ozone was created by UV photons hitting O2 in the upper atmosphere (creating a pair of O- radicals that then attacked a local O2 to form O3). That absorbed the UV, because when the unstable O3 subsequently decayed, it put out IR, not UV. That decay put out O- radicals too, but (30 year old memory here) at a lower energy state, meaning the O- did not have the energy needed to attack the O2 molecules and create another O3, so about the best they could do was find another O- radical and form an O2 molecule.
That is my memory, hence a premise, of the following conclusions:
1. If accurate (and it may not just be my memory, hopefully the science has gotten better too), this makes it seem to me that the ozone layer is an effect, not a cause, of UV absorption. This seems consistent with the following theory: Because O3 is very unstable, any UV photon that hits an O3 molecule is going to break it apart, with very little degradation of the energy of the UV photon (hence, little absorption). So it does not seem to me that O3 protects the Earth much, anyway. What protects the Earth is O2, which takes the high energy UV photon hit and breaks apart, to form O3.
2. If the UV photon does not hit an O2 in the upper atmosphere, it will continue on to Earth, unless it hits an O2 on that path (the O2 gets a lot thicker down this way). Thus, it seems to me the O3 layer will gradually thicken (and get significantly less concentrated), but the actual amount of UV hitting the surface of the earth will be largely unaffected by the O3 layer. If nothing else, the O3 layer may be harder and harder to find, as it extends deeper into the lower atmosphere and at a lower concentration of O3.
3. The premise behind the CFC ban was that CFCs degrade O3, threatening greater ground level UV. However, considering my premise, if CFCs attack O3, does that reduce UV absorption? In fact, it seems that CFCs rapidly degrading O3 is going to turn a lot more O- radicals loose (though perhaps without sufficient energy), to attack more O2 molecules. That could lead to more O3, at which point I cannot remember the equations, and I guess that is just as well because we may not even know the correct ones, right?
Anybody have any thoughts as to what is wrong with my picture?
